The present invention relates to a method for simulating an imaging onto an optical sensor of a coordinate measuring machine for inspecting a measurement object. Furthermore, the present invention relates to a method for optimizing an illumination of a measurement object in a coordinate measuring machine with an optical sensor.
Coordinate measuring machines as such are generally known. They are used in industrial applications for example for quality assurance or measuring components in retro-fit processes or other applications. By means of the coordinate measuring machines, geometries and dimensions of components for the purpose thereof are measured with high accuracy. Various measuring methods differentiated, in principle, into so-called tactile measuring methods and optical measuring methods may be used for determining the coordinates of the components.
Tactile measuring methods probe the component by means of a probe element during the measuring process. By way of example, the probe element is a probe sphere attached to one end of a probe pin. The probe pin with the probe sphere may usually be arranged and aligned in an arbitrary orientation within a measurement area by means of a structural design. By way of example, gantry designs, horizontal arm designs or table designs are known for this purpose.
Optical measuring methods operate without contact, that is to say that the component to be measured, the measurement object, is recorded by means of an optical sensor, for example a camera, and the image data thus obtained are evaluated. A multiplicity of optical measuring methods are known which differ not only in the manner of the image recording but also in the manner of the illumination arrangement. By way of example, deflectometry methods, interferometric methods or chromatic methods, such as the white light sensor method, for example, are known. The optical measuring methods are often accompanied by an electronic image processing and evaluation in order to extract the desired data from the image recordings. Optical sensors may also be arranged in a freely movable and orientable manner within a measurement area by means of a structural design such as a gantry design, horizontal arm design or table design.
All of the abovementioned types of coordinate measuring machines and measuring methods should be understood to be merely by way of example and serve for introduction to the technical field of the present invention. The present invention is concerned with coordinate measuring machines which use optical sensors.
In the case of such coordinate measuring machines with optical sensors, the illumination of a measurement object is of great importance for the accuracy and thus the quality of the measurement. It is generally endeavoured to achieve a homogeneous illumination of appropriate brightness over the entire region of the image recording, in order to be able to detect all details of the measurement object with the highest possible contrast. In this case, the brightness ranges which may be regarded as appropriate are dependent on the type of optical sensor and the brightness ranges proccessible therein.
However, the setting of the illumination in practice requires a high degree of experience on the part of the operating personnel of the coordinate measuring machine or else is very time-consuming, since possibly one or more measurement passes with poor illumination are initially carried out in order to iteratively approximate to the best illumination. Consequently, the operator thus has to carry out a plurality of attempts before arriving at an appropriate illumination which then yields only just usable measurement results. Generally, it is therefore endeavoured to minimize the required prior knowledge and expenditure of time for setting an optimum illumination.
The document DE 10 2009 025 334 A1 discloses a method for ascertaining an ideal appearance of painted surfaces of components such as bodywork components. It is proposed that components to be provided with a multilayered paint are photographed and their optical impression after hypothetical painting is calculated and represented by means of a rendering program. An evaluation is then intended to be made to the effect of whether this calculated optical impression is classified as attractive or not attractive. On the basis of this evaluation, parameters of the paint coating to be applied are then intended to be modified and evaluated by means of recalculations possibly to be performed until the optical impression is classified as “attractive”.
It is an object of the present invention to specify a possibility for simplifying the setting of an illumination in a coordinate measuring machine with an optical sensor.